Richard J. Carr

Prior hypothermia attenuates malignant hyperthermia in susceptible swine

This study was designed to determine the extent by which mild or moderate hypothermia attenuates the triggering of malignant hyperthermia (MH) induced by the combined administration of halothane and succinylcholine.Sixteen susceptible swine were initially anesthetized with nontriggering drugs and then either kept normothermic (approximate equals 38 degrees C, n = 6) or cooled to induce mild (approximate equals 35 degrees C, n = 6), or moderate (approximate equals 33 degrees C, n = 4) hypothermia. Next, after a 30-min control period, the normothermic and mildly hypothermic animals were administered 1 minimum alveolar anesthetic concentration (MAC) halothane followed by a bolus dose of succinylcholine (2 mg/kg). Within 10 min all normothermic animals developed fulminant MH, whereas the onset of MH was slowed or was absent in the mildly hypothermic group. To test whether moderate hypothermia could more effectively minimize the signs of a MH episode, this group of animals was exposed to 1.5 MAC halothane followed 10 min later by a 3-mg/kg bolus of succinylcholine. MH was not induced and anesthesia was then changed to nontriggering drugs (ketamine and pancuronium). The animals were then aggressively rewarmed to 38 degrees C: a slight increase in the ETCO2 was detected, but MH episodes did not spontaneously occur. Subsequently, the readministration of halothane and succinylcholine rapidly provoked fulminant MH. We concluded that the induction of mild hypothermia impairs triggering and reduces the progression of MH induced by the combined administration of halothane and succinylcholine, whereas moderate hypothermia was completely protective and thus could be considered for prophylaxis. (Anesth Analg 1996;82:803-9)

Living liver donor surgery: Report of initial anesthesia experience

Abstract The charts and anesthetic records of 12 patients who donated the left lateral segment of their liver to a related infant or child to treat liver failure were retrospectively reviewed. Blood loss, need for transfusion, fluids administered, surgical length, and perioperative complications were investigated. The records also were examined to determine the hemodynamic stability of patients undergoing donor hepatectomy to assess their need for invasive monitoring. There were no episodes of hypotension or hemodynamic instability. The average operating time was 9.6 ± 1.1 hours. The blood loss was 562 ± 244 mL (range 300 to 1100 mL). Four patients received their own cell saver blood (200 mL, 220 mL, 300 mL, 475 mL), and one patient received 1 U (350 mL) of predonated autologous blood. The average hemoglobin decreased significantly (p = 0.001) from a preoperative value of 14.1 ± 1.2 to 12.3 ± 1.8 g/dL in the recovery room. All patients were extubated in the operating room or recovery room. Patients were discharged home in 6.9 ± 1.3 days (range 5 to 9 days). Living-related liver resection can be performed with noninvasive monitoring and without the need for heterologous blood products.

Clinical assessment of the Augustine GuideTM for endotracheal intubation

The Augustine Guide (AG) allows oral endotracheal intubations to be performed blindly; head and neck manipulation are unnecessary. It is a premolded device designed to fit in a lock and key fashion in the glottis, thus serving as a guide to allow blind laryngeal insertion of an endotracheal tube. Intubation success rate with the AG was studied in 100 adults intubated by the same individual; head and neck were held neutral. Intubations were described as easy if they were successful in the first attempt and difficult when more than one attempt to position the AG was necessary. Endotracheal intubation was successful 94% of the time and was easy in 71%. Repositioning of the AG was necessary in 23%. Patients with jaw abnormalities required repositioning more often (P < 0.05). Esophageal intubation did not occur. Minor trauma was noted in 18% of subjects. The AG is a safe and effective tool for blind orotracheal intubation.

Living related liver transplantation in infants and children: Report of anesthetic care and early postoperative morbidity and mortality

STUDY OBJECTIVE To determine those infants at high risk for perioperative complications and mortality following living, related liver transplantation. DESIGN Retrospective chart review. SETTING Large metropolitan teaching hospital. MEASUREMENTS AND MAIN RESULTS The charts and anesthetic records of the 12 infants and children who received the left lateral hepatic segment from a living relative the past 2 years at our institution were reviewed. The records were examined to determine the causes of perioperative morbidity and to identify patients at high risk for serious complications and mortality. All infants and children (mean +/- SD age, 29+/-30 months; weight, 13.6 +/-6.8 kg) survived the operation (8.3+/-1.7 hours) without intraoperative complications. The average blood loss, including 500 mL of recipient blood used to flush the liver before reperfusion, was 1483 +/-873 mL (119+/-70 mL/kg). Three infants developed portal vein thrombosis, and one of these infants also had hepatic artery thrombosis. The risk of vessel thrombosis was significantly higher (3/3 vs. 0/9; p<0.0045) in infants less than 9 kg body weight, as was the risk of death (2/3 vs. 0/9; p<0.045). Both children who died had vascular thrombosis. Other serious complications were bleeding, 6; infection, 7; acute rejection, 3; and bile leak, 2. CONCLUSIONS Infants and children can successfully undergo living, related liver transplantation. However, the risks of vascular complications and death are greater in infants less than 9 kg body weight.

Differential diagnosis of thyroid crisis and malignant hyperthermia in an anesthetized porcine model.

The intra-operative differential diagnosis between thyroid crisis and malignant hyperthermia can be difficult. Also stress alone can trigger MH. The purposes of this study were: 1) to investigate the metabolic and hemodynamic differences between thyroid crisis and MH, 2) determine how thyroid crisis affects the development of MH, and 3) determine if the stress of thyroid crisis can trigger MH in susceptible individuals. We studied MH susceptible and normal swine. Two groups of animals (MH susceptible and normal) were induced into thyroid crisis (critical core hyperthermia, sustained tachycardia and increase in oxygen consumption) by pretreatment with intraperitoneal triiodothyronine (T3) followed by large hourly intravenous injections of T3. Two similar groups were given intravenous T3 but no pretreatment. These animals did not develop thyroid crisis and served as controls. Thyroid crisis did not result in metabolic changes or rigidity characteristic of an acute episode of MH. When the animals were subsequently challenged with MH triggering agents (halothane plus succinylcholine) dramatic manifestations of fulminant MH episodes (acute serious elevation in exhaled carbon dioxide, arterial CO2, rigidity and acidemia) were noted only in the MH susceptible animals. Although thyroid crisis did not trigger MH in the susceptible animals it did decrease the time to trigger MH (14.1 +/- 7.2 minutes versus 47.2 +/- 17.7 minutes, p < 0.01) in susceptible animals. Hormone induced elevations in temperature and possibly other unidentified factors during thyroid crisis may facilitate the triggering of MH following halothane and succinylcholine challenge.

Evaluation of the Augustine Guide™ for difficult tracheal intubation

Successful tracheal intubation with Augustine Guide ™ (Augustine Medical, Inc., Eden Prairie, MN) in patients with normal airways has recently been described. There are no studies describing Augustine Guide (AG) use in patients with difficult airways. Accordingly, we studied AG intubation in a population of patients with expected difficult airways due to cervical spine pathology, limited mouth opening, obesity, facial trauma or deformity due to previous operation or radiation and in patients with unexpectedly difficult airways. A total of 44 patients were studied. The AG was used as a primary intubating tool in patients with known difficult airways (n = 36) and as a secondary intubating tool in patients with unexpected inability to intubate using conventional direct laryngoscopy (n = 8). Airway difficulty was predicted by history and physical examination. Intubations were performed under general anaesthesia in 40 of the 44 patients studied. In four patients with predictably difficult airways, topical anaesthesia and sedation were used. Backup methods to achieve intubation were available. Thirty-two of the 36 with known or suspected difficult airways were classified as Mallampati Class III or IV. In the remaining eight patients the preoperative examination suggested an easy airway; however, after induction of general anaesthesia, their laryngeal inlet could not be seen using direct laryngoscopy. Using the AG, all were intubated successfully (36/44 at the first attempt, in 8/44 repositioning of the AG to allow successful laryngeal entry of the stylet was necessary). There were no failures or complications secondary to AG use. This study shows that the AG is a useful device for oral tracheal intubation in patients with known or unexpectedly difficult airways.RésuméLa réussite de l’intubation trachéale avec le dispositif d’Augustine (Augustine Guide™, Augustine Medical Inc. MN) chez des patients aux voies aériennes normales a été récemment rapportée. Il n’existe toutefois pas d’étude décrivant l’utilisation du guide d’Augustine (GA) chez des patients dont l’accès aux voies aériennes est difficile. Dans ce but, les auteurs ont évalué l’intubation avec le GA chez des patients dont les voies aériennes étaient présumées difficiles d’accès à cause de pathologies de la colonne cervicale, de limitations à l’ouverture de la bouche, d’obésité, de traumatismes faciaux ou de difformités dues à des interventions antérieures ou aux radiations ainsi que chez des patients non susceptibles de causer de difficultés. L’étude incluait 44 patients. Le GA a été utilisé comme instrument d’intubation principal chez 36 patients connus pour accès difficiles et comme instrument secondaire chez huit patients avec des difficultés imprévisibles d’accès sous laryngoscopie conventionnelle directe. Les difficultés d’accès aux voies aériennes ont été prédites par l’histoire et l’examen physique. Pour quatre patients chez qui des difficultés étaient prévues, l’anesthésie topique et la sédation ont été utilisées. Des méthodes de rechange étaient prévues en cas de besoin. Trente-deux des 36 patients pour lesquels l’accès difficile était connu ou suspecté étaient classifiés HI ou IV sur l’échelle de Mallampati. Chez les huit autres, l’examen préopératoire suggérait un accès facile; cependant, après l’induction de l’anesthésie générale, l’ouverture glottique n’a pu être visualisée sous laryngoscopie directe. Avec la GA, tous ont été intubés avec succès 06/44 au premier essai; chez 8/44, le GA a dû être replacé pour permettre l’introduction du mandrin dans le larynx). Il n’y a pas eu d’échecs ni de complications. Cette étude montre que le GA constitue un dispositif efficace pour l’intubation orotrachéale chez des patients dont l’accès difficile aux voies aériennes est auparavant connu ou inattendu.

Clinical assessment of the Augustine Guide for endotracheal intubation

The Augustine GuideTM (AG) allows oral endotracheal intubations to be performed blindly; head and neck manipulation are unnecessary. It is a premolded device designed to fit in a lock and key fashion in the glottis, thus serving as a guide to allow blind laryngeal insertion of an endotracheal tube. Intubation success rate with the AG was studied in 100 adults intubated by the same individual; head and neck were held neutral. Intubations were described as easy if they were successful in the first attempt and difficult when more than one attempt to position the AG was necessary. Endotracheal intubation was successful 94% of the time and was easy in 71%. Repositioning of the AG was necessary in 23%. Patients with jaw abnormalities required repositioning more often (P < 0.05). Esophageal intubation did not occur. Minor trauma was noted in 18% of subjects. The AG is a safe and effective tool for blind orotracheal intubation.